ASK THE EXPERTS: Low-Cost Wind Electricity

This turbine is mounted on a tower with a height well above the minimum of 30 feet above anything within 500 feet.

Beginner

I am looking for a low-cost batteryless grid-tied wind-electric system for my home in southern California. I already spoke with the city building planning department and the utility, and they both support wind-electric systems.

I consume an average of 192 kWh per month (6.4 kWh per day). I would like to generate at least some of my energy, but not at the level or cost of the systems mentioned in your articles and wind buyer’s guide. It is often windy here at night and our electrical baseline is very low, so I thought that it would be cool to get net metering and sell a little back to the utility. Any suggestions?

Rainer Boelzle • San Diego, California

Your request is common, though problematic. While it’s quite possible to start with a small solar-electric system and add onto it later, wind electricity is generally impractical to approach on a modular basis, and cost effectiveness decreases the smaller you get. The fundamental reason for this is the nature of the wind energy resource.

The power available in the wind increases cubically with increasing wind speed. When comparing a 6 mph wind to a 12 mph wind, the difference in energy is 63 = 216 vs. 123 = 1,728. That’s eight times as much energy potential with a doubling in wind speed. You can see that it’s very important to expose the generator to higher wind speeds.

The other pertinent fact is that wind speed increases as you move away from ground level and its hills, trees, buildings, and other obstructions. Wind speed increases more quickly as you rise above rough surface terrain than over water and other smooth surfaces.

The clear conclusion is that effective wind-electric systems need to include tall towers to get well above any ground obstructions. The standard rule in the industry is to make sure the lower blade tip is at least 30 feet above anything within 500 feet—and higher is better.

So when you contemplate making “a little” wind electricity, you’re often fighting the reality that tall towers are expensive, and that’s what’s needed to get into the viable wind resource. While it’s possible to get lightweight towers (such as anemometer towers) to put very small machines up high, the cost of the tower will be significantly more than the machine. A larger machine with an appropriate tower will get you renewable energy for a lower cost per kWh.

If you opt to put up a very short tower, you will find that there isn’t much wind energy available, regardless of local anecdotal observation or your gut feeling. When there are windy times at those low levels, it’s very turbulent wind, which is hard on wind generators.

Using your 192 kWh per month and a simple formula, we could do some reverse calculations and make some wild guesses about what size of wind generator you might need if you wanted a wind system to provide all of your electricity. Bear in mind that I (and perhaps you, too) have no idea what your resource actually is.

You can multiply the swept area (in square feet) by the average wind speed cubed (in miles per hour), and divide that total by 32,000 to get a rough estimate of average daily kWh production. Dividing by 1,050 instead of 32,000 gives a monthly average. So going the other way, 192 kWh × 1,050 = 201,600. If we stipulate an average wind speed of 10 mph, we see that you’d need a wind generator of about 200 square feet (201,600 ÷ 103) to generate your total kWh requirements in a 10 mph average wind speed resource. This will be a turbine with about a 16-foot-diameter rotor; the machine alone might cost between $15,000 and $20,000 (the full system cost will be several times that).

Bear in mind that to actually get the turbine into a 10 mph resource almost anywhere you might live, you will need a tall tower. If you choose a 30- to 60-foot tower to economize, surprise: You will actually be spending more money per kWh delivered. Looking at our recent wind turbine buyer’s guides, you’ll see that even a 2 mph drop in wind speed will decrease production of a turbine like this by about half. A 50% cut in production means a doubling of the cost per kWh, unless the purchase cost of the system also is cut in half (which it will not be, since shortening the tower is usually only a small reduction in overall system cost). And if your tower is even shorter—closer to the height of surrounding buildings and trees—your turbine won’t even have an 8 mph resource to capture.

The bottom line is that in most cases, trying to go cheaper—by going with a smaller machine or a shorter tower—ends up with more costly electricity. The best way to lower the cost of wind electricity is to choose a large rotor diameter machine and put it on a tall tower. Cutting corners on either swept area (square footage) or wind speed (via shorter towers) will reduce the financial satisfaction. It’s tough news to hear, but perhaps this will save you disappointment later.

Comments (12)

Windside turbines from Finland.. Has been around forever tried and tested but never any mention from anyone. Over 20 yrs experience but yet kept from the American people. Would love to see an unbiased evaluation of the product. You have to wonder if there is something holding this company back from helping people here in the way oil and gas have a hold on other products.

I've received more comment from my wind colleagues about this company. These are colleagues who have been trying to promote realistic and productive wind-electric systems for decades. They and I remain skeptical about verticals in general and most if not all VAWT companies. The operative phrase with most of these companies is, "Oh, are they still in business?"

Windside has toughed it out, but I'm not convinced it's because they are making lots of kilowatt-hours for lots of happy customers. I suspect they are pretty robust and appropriate for navigational buoys in the North Sea. But promoting them for low and roof mounting is typically irresponsible.

One prominent and decades-long user and teacher of wind electricity says:
"Like most VAWTs they are very expensive in relation to their energy production. It's fairly extreme in the case of Windside. The Savonius design is robust unlike the Darrieus, but very slow, and therefore it's expensive to make the alternator. There is no way they can compete with PV outside the Arctic Circle."

And the latest "application" seems to be art: http://www.windside.com/customers_m... . This is OK as far as it goes, but I wish it had no generator, so no one would get confused about the sensibleness of making electricity with this design mounted close to the ground.

But again, my opinion is not the last word. The last word is simple math: How much does it cost installed and maintained, and how many kilowatt-hours does it generate in its lifetime? This logic assumes that your actual goal is clean and economical energy, not yard art or investment capital or sales or greenwashing.

Windside has been around for a long time, but that doesn't necessarily mean they are productive or cost effective turbines. See one U.S. installation that disappointed: http://www2.buildinggreen.com/artic...

One prominent wind colleague of mine says, "...while they may still be in business, the turbines have left a trail of
disaster behind them."

My colleague did some calculations on the turbine project profiled above and came up with these numbers:
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Cost of energy = $38.91/kWh
At $40k installed and $0.12/kWh retail rate for electricity as an MGE customer, the payback is 6485 years.
Not including O&M costs.
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Wow. The key thing to remember with any renewable energy device is that the goal is delivered kilowatt-hours at a reasonable cost. Be careful with the marketing hype and business theories. It all comes down to how much you must invest (capital and maintenance) for how much delivered energy over the life of the system. There is no magic. It's a VERY hard job to make a reliable wind turbine, and you need a great wind site (not to be found near the ground or buildings) to make it worthwhile.

I came across a new / interesting wind turbine design concept on the internet, that I believe has the ability to change all of the current perceived, conventional small wind turbine, rationality. The wind turbine is called SheerWind. In my opinion it is basically a wind turbine situated inside of a hybrid wind tunnel. You all should investigate their concept / design, as in my opinion it is far more than novel or unique. I first experienced this very same concept, when I was a teenager, as the home that my family built, in Michigan, incorporated an enclosed breezeway, situated between the detached three car garage & the house. The breezeway was approximately 20 ft. in length & was venturied. The front yard was in total sunlight / no shade & the back yard was almost entirely shaded, via 80 ft. oak & maple trees. As such the temperature difference between the front & back yards on a hot sunny day was typically 15 - 25 degrees. As such, even on days when there was no wind / airflow to be felt in the front yard, there was "always" @ least a 4-6 mph. breeze / airflow through the breezeway, that was solely attributable to thermal convection. The average annual wind speed through the breezeway was conservatively, approx. 10 - 15 mph. (not exaggerated) As such, my idea has always been to expand upon / improve the design of my fathers first home / breezeway & subsequently situate a wind turbine inside of it. If the breezeway was venturied both horizontally & vertically & if spring actuated dampers / louvers were installed, you would be able to greatly increase / regulate the wind speed, through the breezeway. Just as the SheerWind wind turbine does / accomplishes. I believe if a breezeway is oriented to collect & intensify the prevailing predominant wind direction & if modest thermal convection is also created / generated / designed into it, you can easily, viably generate @ least 40-60 percent of your home electricity needs / requirements. My brother & I would get into heated arguments as to whose turn it was to go get more firewood that was stored out in my fathers breezeway in the winter time, as it could be 10 degrees below zero & the wind would be blowing through the breezeway @ 40 mph. so the wind chill factor was colddddd. I would like to here your thoughts on the SheerWind wind turbine, as in my mind it is primarily the same concept as a venturied breezeway, that I intend to build in the future.

Talk is cheap. Real kilowatt-hours from a wind generator is an entirely different matter.

I recommend waiting for a price tag, a warranty, and a track record before gathering _any_ excitement for a new wind concept or turbine. These "miracle" products come and go, and incautious buyers lose money and hope to them on a regular basis.

Wind energy is hard enough to capture using well known products. There's no silver bullet here, folks -- stick with the tried and true, unless you enjoy gambling...

I have not heard good things about that turbine. But that is probably because they are proponents of putting turbines on buildings, which just does not work very well. Turbines belong on tall towers away from turbulence-causing buildings. So as long as you are going to the expense of putting it on a tall tower, you might as well put up a turbine which is tried and true.

Again, let's see if they can get a certification -- that should tell us what we need to know.

I can understand your doubts, as to SheerWinds claim of 600% increased efficiency, as opposed to a conventional pole mounted wind turbine & the fact that it has not been independently tested, as yet. Try to realize that a pole mounted wind turbine can not have the air flow to the wind turbine, directed, compressed, intensified, ultimately sped up & then regulated / modulated to maintain an optimum wind speed / airflow, for substantially greater durations, thus greatly increasing the overall operating efficiency / electricity generating capacity of the wind turbine. It also can not realize man made / designed / enhanced thermal convection. Also envision this if you will, & we all have experienced it & that is what happens when you open a door on a house only to have a open door on the opposite side of the house, slam shut. In some aspects this is the same principal. In my previous e-mail I conveyed aspects of the breezeway on fathers first home. They were not exaggerations in the least bit. That is why I believe the SheerWind wind turbine to be truly viable. I believe the reason why we have yet to see more of it is because ultimately it is a relatively simple concept / design & they (SheerWind) are currently at a loss of how to market it, as once it gets out what it is. Anybody will be able to build one. I would also suspect that some other entity will potentially figure out the same / similar design / concept, in the very near future. We all shall see. I on the other hand, have already seen / experienced this concept / design in my fathers breezeway. Re-guardless of what transpires in the future with corporate wind turbine technology, I believe a small wind turbine/s situated inside of a properly oriented (predominant prevailing wind direction) venturied breezeway, with passive actuated dampers / louvers & with a greatly accentuated micro-climate / thermal convection can & will generate 40 - 60 percent of the annual electricity demands, for a residential home, especially if the home / structure is also highly energy efficient, i.e. poured concrete. Only time will tell.